The present invention relates to a closing mechanism of an injection molding machine, with a piston-cylinder unit to be pressurized hydraulically, by means of which two partial strokes can be carried out, of which the first can be run through faster than the second, with a displacement tube protruding axially into the cylinder chamber and into an inner cylinder chamber of the piston of the piston-cylinder unit, which tube is fastened to an end wall of the cylinder and is open at it's free end.
Such a closing mechanism is known for example from Austrian reference AT-PS No. 384,578 to the same applicant. With such a closing mechanism, as has been mentioned, a first partial stroke is run through quickly, followed by a second partial stroke in which a larger area of the piston is pressurized, owing to which a greater force can be produced. A practical possibility for the execution of such partial strokes is offered by the displacement tube which protrudes into the cylinder as well as into an inner cylinder of the piston.